The refining industry has been installing sensor based technology on everything from FCC wet gas compressors to valves, distillation column overheads and flares, to monitor conditions potentially affecting plant safety and reliability. These conditions range from mechanical vibration and reactor catalyst deactivation, to corrosion and fouling. Not all refinery units incorporate reactors or prime movers such as the FCCU’s wet gas compressor, but almost all units are vulnerable to fouling and corrosion. In this aspect, Refinery Operations approached NALCO Champion, provider of refinery and petrochemical corrosion and fouling solutions about the use of sensor-based systems to monitor corrosion. Sam Lordo, Nalco Champion marketing director (process North America) responded as follows:
Nalco Champion has been providing new on-line measurement for crude units for the past 4-6 years. The first analyzer introduced was the 3DTfCOS (3DT for Crude Overhead System). This analyzer measures crude tower overhead chloride, pH, iron and ammonia.
Using these measurements the refinery can adjust overhead temperature lower in a reliable manner as the amine and ammonia salting temperature can be determined on a more frequent basis. The COS can control neutralizer, caustic and filmer utilizing its output. It has the capability of receiving remote wireless corrosion monitoring so a comprehensive review of the data is possible. We are also are in the process introducing an on-line salt-in-crude analyzer, which will allow on-line optimization and control of the refinery crude desalter.
One of the management techniques for tramp amines coming into a refinery is with acid injection in the desalter. While desalter acidification is a solution, it can create issues when not properly controlled. Since the control KPI is the pH of the desalter water effluent, Nalco Champion developed an on-line pH analyzer that is robust enough to operate reliably. By having a reliable pH we can control the acid to meet the target operating range of the desalter brine pH. This analyzer also has the capability to detect oil under-carry and corrosivity of the desalter brine. The oil under-carry feature is for routine control and mitigates issues that could create wastewater unit upsets, either through detection and alarm or by adjusting the chemical additive program or implementation of diversion actions (into a tank). The corrosion probe is used to adjust the corrosion inhibitor that is routinely used as part of a desalter acidification program.